In the full term neonate, the ductus arteriosus constricts rapidly after delivery in order to separate the pulmonary from the systemic circulations. Failure of the ductus to close after birth results in significant morbidity: chronic lung disease, necrotizing enterocolitis, etc. Permanent closure of the ductus arteriosus is accomplished by extensive remodeling of the vessel wall: smooth muscle cells from the muscle media migrate into the intima to form intimal wounds that occlude the lumen. This process frequently does not take place in the premature human infant. As ductus smooth muscle cells migrate through the surrounding extracellular matrix they interact with specific glycoproteins: fibronectin, laminin, collagen I and IV, and vitronectin. This interaction is mediated by multiple cell surface adhesion receptors of the integrin heterodimer superfamily. The overall specific aims of this proposal are: 1) To characterize the integrin receptors possessed by isolated smooth muscle cells derived from the fetal sheep ductus arteriosus, and to see how they differ from cells derived from the postnatal closed ductus and the adjacent aorta. This will be accomplished by Northern blotting and polymerase chain reaction of cellular RNA; by radiolabeling smooth muscle cells in culture and using ligand-affinity chromatography, immunoprecipitation, and SDS-PAGE techniques to identify the receptors for individual extracellular matrix components; and by radioligand binding studies. Immunofluorescence of single smooth muscle cells will identify the location of the receptors in stationary and migrating cells; 2) To identify the role of the integrin receptors in cell behavior by using specific antibodies to interfere with the ability of the cell to adhere to, migrate over and invade, as well as rearrange individual extracellular matrix components. 3) To identify factors that modulate the ductus smooth muscle integrin profile and to examine how these affect cell behavior. 4) To examine the differences in the expression of matrix proteins, integrin receptors, and hormonal factors in whole ductus tissue derived from fetal and postnatal closed ductus arteriosus. These studies should increase our understanding of how smooth muscle cells remodel the ductus, after birth; future investigations can then examine how the preterm ductus differs from the full term ductus and why it does not undergo the same remodeling.